Paul Manafort, the political operative who for months led Donald Trump's winning presidential campaign, has been found guilty of eight financial crimes.

It is the first trial victory of the special counsel investigation into the president's associates. A judge declared a mistrial on 10 other counts the jury could not agree on.

The verdict was part a stunning one-two punch of bad news for the White House, coming as the president's former lawyer, Michael Cohen, was pleading guilty in New York as part of a separate deal with prosecutors.

The jury returned the decision after deliberating four days on the charges of tax evasion and bank fraud against the former Trump campaign chairman.

The outcome almost certainly guarantees years of prison for Manafort and established the ability of special counsel Robert Mueller's team to persuade a jury of average citizens despite months of partisan attacks - including from President Trump - on the investigation's integrity.

The verdict raised immediate questions of whether the president would seek to pardon Manafort, the lone American charged by Mr Mueller to opt for trial instead of cooperate.

The president has not revealed his thinking but spoke sympathetically throughout the trial of his onetime aide, at one point suggesting he had been treated worse than gangster Al Capone.

The more-than-two-week trial, presided over by US District Judge TS Ellis III, has captured President Trump's attention as he works to undermine Mr Mueller's investigation through a constant Twitter barrage and increasingly antagonistic statements from his lawyer-spokesman, Rudy Giuliani.

But President Trump and his campaign were only a small part of Manafort's trial, as jurors instead heard days of testimony about Manafort's finances and what prosecutors say was a years-long tax-evasion and fraud scheme.

(Image: Justin Sullivan/Getty Images)

Manafort decided not to put on any witnesses or testify himself in the trial. His lawyers said he made the decision because he did not believe the government had met its burden of proof.

President Trump later said that the Manafort conviction "has nothing to do with Russian collusion", and brand the move "a disgrace".